The evolution of evaporating charged black holes is complicated to model in
general, but is nevertheless important since the hints to the Information Loss
Paradox and its recent firewall incarnation may lie in understanding more
generic geometries than that of Schwarzschild spacetime. Fortunately, for
sufficiently large asymptotically flat Reissner-Nordstrom black holes, the
evaporation process can be modeled via a system of coupled linear ordinary
differential equations, with charge loss rate governed by Schwinger
pair-production process. The same model can be generalized to study the
evaporation of AdS Reissner-Nordstrom black holes with flat horizon. It was
recently found that such black holes always evolve towards extremality since
charge loss is inefficient. This property is completely opposite to the
asymptotically flat case in which the black hole eventually loses its charges
and tends towards Schwarzschild limit. We clarify the underlying reason for
this different behavior.Comment: References updated. Published in JHE